Fast burning double-base propellant

ABSTRACT

Double-base propellant compositions employing 1-nitro-2carboranylpropene (NIPC) as a catalyst are stable compositions which burn at increased rate.

States Patent [191 ill Feb. 12, 1974 FAST BURNING DOUBLE-BASE PROPELLANT [56] References Cited [75] Inventor: William E. Hill, Huntsville, Ala. IT ATE PATENT 173] Assignee: The United States of America as 2:326:72 if :32; te l l49/33 X represented by the Secretary of the 3375282 3 1968 g a l 49 X Army, Washington, D.C. l man at a' [22] Filed: Apr. 16, 1969 Primary ExaminerStephen J. Lechert, Jr.

I Attorney, Agent, or Firm-Edward J. Kelly; Herbert [211 App! 8l7617 Berl; James T. Deaton [52 US. Cl 149/19, 149/20, 149/22, [57] ABSTRACT 149/ 2 3 7 7 6 Double-base propellant compositions employing 51 I t C] C66) 11/00 1-nitro-2-carborany1propene (NIPC) as a catalyst are 38 99 39 stable compositions which burn at increased rate.

5 Claims, No Drawings 1 ll FAST BURNING DOUBLE-BASE PROPELLANT BACKGROUND OF THE INVENTION This invention relates to solid double-base propellant compositions generally comprising the ingredients: nitrocellulose, an inorganic oxidizing salt, a plasticizer, stabilizer, burning rate modifier or catalyst, curing agent, processing aids, and more recently, metal as fuel.

Earlier prior art double-base propellant compositions generally have been comprised of about 50 weight percent nitrocellulose, plasticizer about 35 to 45 weight percent, curing agents about 1 to 5 weight percent, concentrations of other materials in amounts of 0.1 weight percent to 2.5 weight percent (e.g., stabilizers, such as 2-nitrodiphenylamine 1-2 percent, candelilla wax 0.2 weight percent, and metallic salts as burning rate modifiers), and optionally metal fuels.

More recently the trend has been to use powdered metal as a fuel to thereby increase the specific impulse of the propellant. Also,the use of special burning rate catalyst have been successful in obtaining marginal increase in burning rate. Thus, solid propellants having higher and higherburning rates have been sought after on a continuous basis because of the need for higher specific impulse propulsion systems in present day rocketry.

Solid propellants are generally classified into two groups: homogeneous propellants and composite propellants. Composite propellants consists of propellants 'wherein solid oxidizers and other-solid additives are dispersed within an organic binder such as polybutadiene-acrylic acid polymers, polysulfide polymer, polyester heteropolymerized with unsaturated olefins, and polyurethanes. The homogenous propellant consists of gel type propellants of single, double, and triple base type. The present invention particularly relates to double-base propellants containing nitrocellulose, a plasticizer, metal fuel, inorganic oxidizer, stabilizers, processing aid, cross-linking agent, and burning rate catalyst. The double-base propellant compositions of this invention are particularly attractive because of the high burning rates and stabilities thereof.

In the past burning rate catalysts have included organo-metallic compounds, metallic oxides, metal fibers or metal staples, and other components which promote burning in a number of ways which include surface phenomena and decomposition rate control of the oxidizers. The burning rates of the prior art propellants have not reached the high rates desirable for present propulsion systems. Also, the processing problems and problems of migration of the catalyst have been some of the problems of vital concern associated with the prior art compositions. These problems have resulted in uneven burning rates or lower burning rates during a particular phase of the burning cycle.

The present invention has as its principal object to provide a fast burning rate double-base propellant which is both stable and fast burning.

Another object of this invention is to provide doublebase-propellants which can employ proven conventional prior art ingredients in combination with a novel nitro derivative of a carborane compound to achieve burning rates in excess of five inches per second at 2,000 psi.

The novel nitro derivative of l-isopropenylcarborane can be produced according to the following procedure:

10 grams of isopropenylcarborane and 250 milliliters of ether are combined into a three necked flask and allowed to react with a slight excess of N 0 at room temperature. After 2 hours, the reaction is quenched with aqueous sodium bicarbonate and the solvent removed. The crude oil is chromatographed over silica gel to yield 1-nitro-2-carboranylpropene' (NIPC) 40 percent and a nitro alcohol about 60 percent.

For further information on the process to produce (NIPC) refer to copending application Ser. No. 798,269, filed Feb. 5, 1969.

NIPC has been found to be compatible with nitrocellulose. Of course, compatibility is a primary concern of any ingredient selected for propellant use. The amount of NIPC used as a catalyst can vary considerably, depending on the burning rates desired. For example, burning rates of 3.90 in./sec. is obtainable when about 6.1 weight percent of NIPC is used. The burning rate increase to about 5.90 in./sec. is achieved when about 12.2 weight percent of NIPC is used.

In addition to NIPC the solid propellant compositions of this invention contain nitrocellulose in amounts from about 5 to about 20 weight percent. Plasticizers such as nitroglycerin, triacetin, adiponitrile, and TEGDN (triethyleneglycoldinitrate) in amounts of about 10 to about 30 weight percent may be used. Inorganic oxidizing salts in amounts of about 35 to about 52 weight percent are used. Inorganic oxidizing salts such as ammonium, alkali metal, and alkaline earth metal-salts of nitric, perchloric, and chloric acids, and mixtures thereof are suitable oxidizing salts for use in this invention. Powdered metals such as aluminum, magnesium, titanium, zirconium, and boron are suitable for use in the propellant composition in amounts of from about 5 to about 20 weight percent. Aluminum is the preferred metal. Stabilizers such asresorcinol and 2-nitrodiphenylamine in amounts of about 0.5 to about 2 weight percent are generally used in propellants containing nitrocellulose and/or nitroglycerin. Plasticizers perform functions of curing propellant by assisting in cross-linking, chain extending, and chain branching reactions which directly result in imparting desirable physical properties to the propellant when cured. The plasticizer type com pounds described are used in the propellant compositions of this invention in amounts of about 3 to about 10 weight percent. Compounds to impart physical properties to propellants when cured include adiponitrile, di-n-propyladipate, triacetin, and the like.

Description of the Preferred Embodiments: The propellant compositions set forth below as composition A and composition B are equally attractive, and the burning rates obtained illustrate that the amount of NIPC used in the composition directly influences the burning rate. Composition C is the control sample. The propellant composition selected depends on the requirements of the system where used.

EXAMPLE 1 Composition A The burning rate of composition A at 2,000 psi is 5.90 in./sec.

EXAMPLE ll Composition B Component Nitrocellulose TEGDN Aluminum Ammonium Perchlorate Adiponitrile NlPC Resorcinol The burning rate of composition B at 2,000 psi is 3.90 in./sec.

Control for Example I & ll, Compositions A & B

Composition C The burning rate of composition C, control sample, 25

at 2,000 psi is 2.00 in./sec.

The procedure for propellant mixing can be varied according to the particular facility available. Generally, the nitrocellulose, plasticizer, catalyst, and stabilizer are mixed together until a homogenous mixture is obtained. After the mixture is uniform, dried powdered metal is added and the mass mixed until the metal particles are wetted. The dried inorganic oxidizing salt, additional stabilizers, and special additives desired are next added and the mixture is mixed under vacuum at about l-150F for about 0.5-1 .5 hours or until a homogeneous mixture is obtained. The adiponitrile or other materials such as cross-linking agents, which contribute to the propellant physical properties when cured, are then added and the mixing continued for about 0.5 hour. The resulting mixture is cast into a suitable mold or rocket motor to form the propellant grain. The grain is cured for several days at about 120 to 150F until the cure is accomplished.

The burning rate catalyst, NIPC, of this invention is easily blended with the other propellant ingredients. The use of NIPC in amounts from about 5 weight percent to about weight percent of the propellant composition provides a wide range of burning rates and varied compositions with a multitude of performances.

The stability shown toward nitrocellulose and the other components commonly used in double base formulations makes NIPC particularly attractive for the use described.

I claim:

1. A solid propellant composition comprising at least one inorganic oxidizing salt, plasticizers, metal additive, nitrocellulose, and l-nitro-2-carboranylpropene.

2. The propellant composition of claim 1 and wherein said inorganic oxidizing salt is selected from ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric, and chloric acids, and mixtures thereof in an amount from about 35 to about 52 weight percent; said plasticizers are selected from nitroglycerin, triacetin, adiponitrile, and triethyleneglycoldinitrate in an amount from about 10 to about 30 weight percent; said metal additive is selected from aluminum, magnesium, titanium, zirconium, and boron in amount from about 5 to about 20 weight percent; and wherein said l-nitro-2-carboranylpropene is present in amount from about 5 to about 25 weight percent.

3. The propellant composition of claim 2 and also comprising a stabilizer selected from resorcinol and 2- nitrodiphenylamine in amounts from about 0.5 to about 2 weight percent.

4. The propellant composition of claim 3 and wherein said nitrocellulose is present in an amount of about 10.6 weight percent; said plasticizers comprise triethyleneglycoldinitrate in an amount of about l3.2 weight percent and adiponitrile in an amount of about 3.3 weight percent; said metal additive is aluminum present in an amount of about 10.0 weight percent; said inorganic oxidizing salt is ammonium perchlorate present in an amount of about 50.0 weight percent; said stabilizer is resorcinol present in an amount of about 0.7 weight percent; and said l-nitro-2-carboranylpropene is present in an amount of about 12.2 weight percent.

5. The propellant composition of claim 3 and wherein said nitrocellulose is present in an amount of about 10.6 weight percent; said plasticizers comprise triethyleneglycoldinitrate in an amount of about 17.1 weight percent and adiponitrile in an amount of about 1.7 weight percent; said metal additive is present in an amount of about 13.8 weight percent; and said l-nitro-2-carboranylpropene is present in an amount of about 6.1 weight percent. 

2. The propellant composition of claim 1 and wherein said inorganic oxidizing salt is selected from ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric, and chloric acids, and mixtures thereof in an amount from about 35 to about 52 weight percent; said plasticizers are selected from nitroglycerin, triacetin, adiponitrile, and triethyleneglycoldinitrate in an amount from about 10 to about 30 weight percent; said metal additive is selected from aluminum, magnesium, titanium, zirconium, and boron in amount from about 5 to about 20 weight percent; and wherein said 1-nitro-2-carboranylpropene is present in amount from about 5 to about 25 weight percent.
 3. The propellant composition of claim 2 and also comprising a stabilizer selected from resorcinol and 2-nitrodiphenylamine in amounts from about 0.5 to about 2 weight percent.
 4. The propellant composition of claim 3 and wherein said nitrocellulose is present in an amount of about 10.6 weight percent; said plasticizers comprise triethyleneglycoldinitrate in an amount of about 13.2 weight percent and adiponitrile in an amount of about 3.3 weight percent; said metal additive is aluminum present in an amount of about 10.0 weight percent; said inorganic oxidizing salt is ammonium perchlorate present in an amount of about 50.0 weight percent; said stabilizer is resorcinol present in an amount of about 0.7 weight percent; and said 1-nitro-2-carboranylpropene is present in an amount of about 12.2 weight percent.
 5. The propellant composition of claim 3 and wherein said nitrocellulose is present in an amount of about 10.6 weight percent; said plasticizers compriSe triethyleneglycoldinitrate in an amount of about 17.1 weight percent and adiponitrile in an amount of about 1.7 weight percent; said metal additive is present in an amount of about 13.8 weight percent; and said 1-nitro-2-carboranylpropene is present in an amount of about 6.1 weight percent. 